Area cutting method

Abstract

The present invention relates to an area cutting method for cutting an area (AR) delimited by a curve (OLC) of an external shape and at least two closed curves (INC 1 , INC 2 ) which lie within the curve of the external shape. The area cutting method has a step of calculating first and second offset curves (INF 1 , INF 2 ) offset outwardly from the respective closed curves (INC 1 , INC 2 ) by an amount dependent upon tool diameter, a step of checking whether the offset curves intersect each other, a step of ascertaining that an overlap portion (CSA) incapable of being area-cut exists when the offset curves intersect each other, and a step of cutting only an area from which the portion (CSA) incapable of being area-cut is omitted when the overlap portion exists.

What is claimed is: 
     
       1. An area cutting determining method for determining an area for cutting delimited by a curve of an external shape and at least two closed curves which lie within said curve of the external shape, comprising the steps of: producing offset curves outwardly from respective ones of said closed curves by an amount dependent upon tool diameter;   checking whether the offset curves intersect one another;   ascertaining that an overlap portion incapable of being area-cut exists when the offset curves intersect one another;   entering area cutting data necessary for performing area cutting based on unidirectional cutting or back-and-forth cutting including a cutting path shift direction and a shift amount;   producing a straight line, which specifies an i-th cutting path PTi, from the cutting path shift direction and the shift amount contained in said area cutting data;   obtaining points Pi, Qi at which said straight line intersects an offset curve obtained by inwardly offsetting the curve of the external shape, and point Ri, Si; Ti, Ui at which said straight line intersects each of said offset curves, respectively; and   cutting an area from which said overlap position incapable of being area cut is omitted by: moving the tool in a cutting-feed mode along the i-th cutting path from the machining starting point Pi to the intersection point Ri;   moving the tool in the cutting-feed mode along an offset curve containing said intersection point Ri;   moving the tool in the cutting-feed mode along the i-th cutting path after arrival thereat when the tool arrives at the i-th cutting path before arriving at a different offset curve;   moving the tool along the other offset curve after arrival thereat when the tool arrives at a different   moving the tool along the i-th cutting path to the machining end point Qi.